The drug tacrine is indicated for the treatment of neurological diseases, including Alzheimer's disease. The neurological-Alzheimer's disease is a progressive, irreversible brain disorder that strikes more frequently with advancing age. The common symptoms of this neurological disease generally include memory loss, confusion, impaired judgment, personality changes, and the loss of language skills. There is, during the course of the disease, a dependence on others to assist the patient in performing tasks such as taking medicine. The average length of the illness is seven years, but it can last fifteen or more years. Presently, research indicates the symptoms of Alzheimer's disease are the result of the loss of nerve cell function in distinct areas of the brain. Alzheimer's disease affects an estimated four-million people, and most cases occur after age sixty; however, the disease affects some individuals in their forties and fifties, usually affecting about ten percent of people over sixty-five. Alzheimer's disease affects all people, and the disease is not restricted to any race, gender, or socioeconomic class.
The drug tacrine for treating neurological diseases, including Alzheimer's disease, is disclosed in U.S. Pat. No. 4,816,456 issued to Summers. The patent teaches the drug tacrine can be administered by standard noncontrolled tablet, pill, powder, elixir, solution, suppository, ointment, cream and capsule, which are dose-dumping conventional forms. The conventional forms deliver the drug by dose-dumping, and this leads to uneven dosing of drug, to uneven blood levels of the drug characterized by peaks and valleys, and accordingly, this does not provide controlled-rate therapy over an extended period of time. Presently, tacrine is administered many times a day because tacrine has a half-life of about three hours. The prior-art dosing patterns and the half-life characteristics of tacrine dictate of the need for an unique dosage form that can administer tacrine over an extended therapeutic time to provide continuous therapy and beneficial therapy to an Alzheimer's patient. The medical history of Alzheimer's disease is known in Current Therapy, Conn, pp. 831-835 (1994).
The prior art provided dosage forms that can administer many drugs for extended-controlled therapy. For example, in U.S. Pat. Nos. 3,845,770 and 3,916,899 issued to Theeuwes and Higuchi, in U.S. Pat. No. 4,327,725 issued to Cortese and Theeuwes, and in U.S. Pat. Nos. 4,612,008, 4,765,989, and 4,783,337 issued to Wong, Barclay, Deters and Theeuwes, a dosage form is disclosed that provides therapy by pressure generated inside the dosage form. The dosage form of these patents operates successfully for delivering a drug that develops a high pressure gradient across a semipermeable membrane. The drug tacrine, however, possesses a low osmotic pressure, which dictates against providing an osmotic dosage form for use in the gastrointestinal tract. The gastrointestinal tract has a high osmotic pressure, and this speaks against an osmotic dosage form comprising tacrine as this environment can adversely affect the delivery of tacrine, from the dosage form in this environment.
It is immediately apparent in light of the above presentation that an urgent need exists for a dosage form endowed with the necessary physical-chemical properties for delivering tacrine. The need exists for a dosage form for delivering tacrine at a controlled-rate in a continuous dose in a therapeutic tacrine range governed by the dosage form, while simultaneously providing the beneficial tacrine therapy. It will be appreciated by those versed in the drug dispensing art that if such a dosage form is provided that can administer tacrine in the desired delivery program, the dosage form or a therapeutic composition in the dosage form comprising tacrine would represent an advancement and valuable contribution in Alzheimer therapy.